Conventionally, many semiconductor integrated circuit devices include an overcurrent protection circuit which is one of abnormality protection circuits. For example, an in-vehicle IPD (Intelligent Power Device) includes an overcurrent protection circuit so as to prevent the device from being destroyed even when a load connected to a power transistor is short-circuited.
By the way, there is also a load (a capacitive load, etc.) connected to the power transistor that requires a large output current instantaneously in a normal operation. Therefore, the conventional overcurrent protection circuit adopts a current control mode of limiting an output current to a predetermined upper limit value or less, instead of cutting off the output current at the time of short-circuiting of the load, in which a determination on whether to cut off the output current is delegated to a temperature protection circuit (a so-called thermal shutdown circuit) that detects a device temperature abnormality.
In many cases, the temperature protection circuit is of a self-resetting type of forcibly turning off the power transistor when a junction temperature of the device is higher than an abnormality detection value (for example, 175 degrees C.) while releasing the forced-off of the power transistor when the junction temperature is lower than an abnormality release value (for example, 150 degrees C.).
However, in the case of adopting the above-described conventional abnormality protection method (the current control mode+the self-resetting type thermal shutdown), at the time of load short-circuit, the device will continue to operate in a high temperature range (for example, 150 degrees C. to 175 degrees C.) where the detection and release of temperature abnormality with an overcurrent are repeated. Therefore, there is a room for further improvement on the safety of the device.
In particular, in recent years, it has been required to comply with ISO 26262 (the international standards for electric/electronic-related functional safety of vehicles) for in-vehicle ICs and a higher reliability design becomes also important for in-vehicle IPD.